U.S. administration officials signaled Monday a peace deal between Russia and Ukraine may be closer than ever.

Russian Deputy Foreign Minister Sergey Ryabkov told ABC News during an exclusive interview in Moscow on Monday that he believes the warring parties are close to a deal.

Two U.S. officials who spoke on the condition of anonymity said the arrangement would be similar to the NATO mutual defense agreement. But crucial details remain unsettled as negotiators seek a deal that Russia will approve.

A 1,000-strong "dark fleet" of rogue tankers evading sanctions has become a new target for the U.S. and Ukraine, according to a senior maritime intelligence analyst.

Two days of intense negotiations between Ukraine, the U.S. and European officials resulted in clear progress on security guarantees for Ukraine but left significant gaps on the issue of territory, U.S. officials told reporters on Monday.

While US officials talked up progress in Berlin, there was little detail on how the issue of Ukraine's sovereignty would be resolved.

Ukrainian President Volodymyr Zelensky flew to Berlin on Sunday for two days of talks with European leaders and US President Donald Trump's envoys on ending the almost four-year war with Russia.While fighting raged on in Ukraine,